Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/0005—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor characterised by the material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
  • B29C2949/22—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at neck portion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
  • B29C2949/24—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at flange portion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
  • B29C2949/26—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at body portion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
  • B29C2949/28—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at bottom portion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/30—Preforms or parisons made of several components
  • B29C2949/3024—Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/30—Preforms or parisons made of several components
  • B29C2949/3032—Preforms or parisons made of several components having components being injected
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/30—Preforms or parisons made of several components
  • B29C2949/3048—Preforms or parisons made of several components having components being thermoformed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/42—Component parts, details or accessories; Auxiliary operations
  • B29C49/64—Heating or cooling preforms, parisons or blown articles
  • B29C49/6604—Thermal conditioning of the blown article
  • B29C49/6605—Heating the article, e.g. for hot fill
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material

Definitions

• This invention relates to the production of hollow articles, and more particularly to the production of such articles that are substantially transparent.
• thermoplastic resin composition The production of hollow articles, such as containers for example, by blow-moulding a thermoplastic resin composition is well known.
• resins as polyethylene or polyvinyl chloride have been traditionally used for this purpose but more recently polyesters such as polyethylene terephthalate (PET) have been introduced, particularly for the production of bottles for carbonated beverages and other liquids.
• PET polyethylene terephthalate
• polyethylene terephthalate containers are eminently suitable for use at ordinary temperatures, they need to be annealed before they can be filled with hot materials or subjected to pasteurisation temperatures. Annealing reduces the production rate and introduces extra costs, and may not be sufficient to give the required heat resistance.
• EP-B-0,042,724 (Ethyl Corporation) describes a thermoplastic moulding composition which comprises, in intimate admixture: (a) a polyethylene terephthalate and (b) a copolymer of a vinyl aromatic compound and an alpha, beta-unsaturated cyclic anhydride, said composition having a heat deflection temperature of about 84°C or above at 1.82 MPa as measured by ASTM D 648-72.
• GB-A-2076832 (Celanese Corporation) describes blends of polyethylene terephthalate based polyesters and styrene maleic anhydride copolymers in a weight ratio of 99:1 to 50:50, which are stated to exhibit improved mouldability and improved adhesive properties to a variety of substrates. Specifically, lower mould temperatures can be employed when injection moulding the blends.
• transparent blow-moulded hollow articles can be in fact made from such compositions if the preform is maintained at a relatively high temperature from the time it is made until the time it is blown into the article, so that crystallisation of the preform is prevented in this way rather than by chilling the preform mould.
• extrusion-blow-moulding can be employed with these compositions (even though it cannot with polyethylene terephthalate itself) and is very suitable for a process in accordance with this invention.
• the process of this invention is one for producing a blow-moulded hollow article from a polyester composition in which a preform is made and thereafter expanded by means of differential fluid pressure into contact with a hollow mould of shape corresponding to that of the desired article, characterised in that (a) the polyester composition comprises polyethylene terephthalate (PET) and a styrene maleic anhydride copolymer (SMA) in a weight ratio of from 10 to 50 parts of SMA per hundred parts of (SMA + PET) and (b) the preform is maintained at between 180 and 250°C substantially to prevent it from crystallising before it is expanded, whereby (c) the hollow article is substantially transparent.
• PET polyethylene terephthalate
• SMA styrene maleic anhydride copolymer
• the invention also comprises a blow-moulded hollow article made from a polyester composition characterised in that (a) the composition comprises polyethylene terephthalate (PET) and a styrene maleic anhydride copolymer (SMA) in a weight ratio of from 10 to 50 parts of SMA per hundred parts of (SMA + PET) and (b) the article is substantially transparent.
• a the composition comprises polyethylene terephthalate (PET) and a styrene maleic anhydride copolymer (SMA) in a weight ratio of from 10 to 50 parts of SMA per hundred parts of (SMA + PET) and (b) the article is substantially transparent.
• PET polyethylene terephthalate
• SMA styrene maleic anhydride copolymer
• the article is capable of being filled with a liquid at a temperature of 75 to 110°C without deformation.
• the PET can be any of the PET resins sold for blow-moulding. Suitable examples are for example described in US-A-4,483,949 "Glycol modified PET” (PETG) can be used if desired; this contains blocks of polyether within the polymer molecule.
• PET resins sold for blow-moulding Suitable examples are for example described in US-A-4,483,949 "Glycol modified PET” (PETG) can be used if desired; this contains blocks of polyether within the polymer molecule.
• the SMA preferably contains from 10 to 30% by weight of maleic anhydride, based on the weight of the SMA. A preferred proportion is from 15 to 30% by weight.
• An additonal copolymerised monomer for example methyl methacrylate (MMA), can be present if desired, and the proportion of such additional monomer can usefully be adjusted so that the SMA has substantially the same refractive index as the PET, for it has been found that a difference in refractive index can cause the formation of a slight haziness in the final article.
• MMA methyl methacrylate
• the refractive index of SMA containing 75% of styrene, and 25% of maleic anhydride by weight together with from 0 to 7% of MMA changes from 1.575 to 1.57 as the proportion of MMA is increased over the range 0% to 7%.
• a proportion of MMA of below 2% by weight would thus be appropriate in order to achieve maximum transparency in this particular example.
• the styrene can be wholly or partly replaced by a derivative of styrene such as alpha-methylstyrene, vinyl­toluene or a halostyrene.
• Rubber-modification of the SMA leads to a great reduction in the transparency of the hollow article and is not desirable.
• the amount of SMA in the polyester composition is preferably from 10 to 40% of the composition, more preferably from 15 to 30%, by weight.
• compositions can be blended together by any convenient method, for example by extrusion blending or by dry blending of particles.
• Additives such as colouring agents, antioxidants or lubricants can be incorporated.
• the preform In carrying out the blow moulding process it is important to blow the preform at a temperature above the transition temperature of SMA (Tg) in order to maintain the clarity. If the blowing process occurs below the Tg of SMA the hollow article is white.
• Tg transition temperature of SMA
• the Tg for SMA with maleic anhydride within the preferred range varies from 120°C to 170°C.
• the maximum crystallisation rate of PET is between 100°C and 230°C with the peak around 165°C.
• the mould should not be chilled, a mould temperature of 20 to 40°C often being suitable.
• the preform can be maintained at the necessary temperature by any convenient means; for example by effecting so rapid a transfer from the mould to the place where it is blown that it does not have time to cool below SMA Tg, or by heating (for example by infra-red radiation) during such transfer.
• One such method uses an injection blow-moulding machine having a carousel for effecting the transfer and infra-red lamps to heat the preforms. Conventionally such lamps are employed to reheat preforms of PET (i.e., without SMA) made using a chilled mould.
• the preform of PET/SMA issues from a non -chilled mould and never cools down sufficiently to be below SMA Tg, as we have found it does do with a chilled mould
• stretch-blow-moulding employs a preform that is substantially flat, for example a disc stamped from a sheet, that is then pushed into a hollow shape by means of a plunger.
• stretch-blow-­moulding employs a preform that is substantially flat, for example a disc stamped from a sheet, that is then pushed into a hollow shape by means of a plunger.
• articles for example bottles, have a light transmission ("transparency") of at least 50%. Very often, a transparency of 70% or more is achieved, while from 60% to 70% is most usual.
• the articles can be filled with hot liquids without significant deformation, and for example hot water at 80 to 85°C can be poured into a bottle of 1 litre capacity and weighing 35 g, without any observable effects.
• Articles according to the invention are useful as containers, for example, particularly for hot-filled or pasteurisable contents. However, they are also useful as parts for household fittings such as lighting fittings, toys, ornaments and so on.
• Dry blends of 80% PER Arnite D04-300 (intrinsic viscosity 0.85) from Akzo Chemie with 20% SMA terpolymer at 25% MA were prepared just before injection moulding.
• the PET was received from Akzo in sealed bags ready to use while the SMA was dried for 3 hours at 70°C in a Somos hopper dier.
• the blends were injected in a one step injection blow moulding machine Bekum SBM 315 E30.
• the containers are produced in three stages :
• Nozzle temperature 290°C
• Preform mould temperature 10 to 25°C. Core uncooled (no cooling air).
• Bottle mould temperature 35°C Injection time + cooling time : 3.5 seconds (4 bottles per minute)
• Melt temperature 260°C
• the bottles obtained were transparent in the body and the neck. They could be filled with water at 85°C without deformation.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)

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Publications (2)

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Family Applications (1)

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Cited By (2)

Citations (8)

• 1986
  • 1986-12-30 GB GB868631015A patent/GB8631015D0/en active Pending
• 1987
  • 1987-12-29 EP EP87870205A patent/EP0273896A3/de not_active Ceased

Patent Citations (8)

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